The present invention relates generally to packaging materials, and more specifically to an improved double bag construction for packaging meats and other foods for longer term preservation during storage and transport.
Several different forms of packaging are known for containing meats and other foods under refrigerated conditions in order to preserve them during storage and transport until they are ready to be marketed to the consumer. For meat in particular, it is important not only to preserve its freshness, but also its red color, which is associated by consumers with freshness.
It is well known that fresh meat quality may be maintained longer under anaerobic conditions than aerobic conditions. While fresh, such meat has a purple-red color that relatively few consumers associate with freshness. However, when oxygenated by reexposure to air to convert myoglobins in the meat to oxymyoglobins, the color quickly changes to the generally acceptable bright red color. Therefore, any packaging must minimize exposure of the meat during storage and transportation to atmospheric oxygen, while permitting the meat to bloom to its full red color upon removal of the packaging prior to its placement for display and sale to the consumer.
One such form of packaging has constituted an inner container constructed from, e.g., chip board or cheese cloth, which in turn is contained by an oxygen impermeable, outer flexible bag. However, several disadvantages are created by such a construction. First, the inner chip board or cheese cloth container readily absorbs blood and other liquid materials found in the foods to be packaged, thereby allowing bone and other sharp, rigid matter easily to penetrate the inner container and outer bag during the vacuuming procedure needed to remove air during the packaging process, as well as its subsequent shipping and handling. This, in turn, ruins the very anaerobic conditions needed for preservation. Second, the inner container absorbs oxygen and other gasses before the vacuuming and flushing procedures, which dilutes the gas (usually carbon dioxide or nitrogen) flushed into the bag that is needed to replace the exhausted oxygen gas. Third, an inner container made from chip board is relatively inflexible, thereby increasing storage and shipping space demands, as well as being heavier than plastic, which translates into increased shipping weights and the costs associated therewith.
U.S. Pat. No. 3,574,642 issued to Weinke discloses another packaging construction for meats in the form of an inner oxygen-permeable bag which may be either gas flushed or evacuated, and an outer oxygen-impermeable bag, which may likewise be gas flushed or evacuated. Upon placement of the meat into the inner bag, the bag is heat sealed after removal of oxygen. The inner bag is then inserted into the outer bag from which all oxygen is removed, and the outer bag is then heat sealed. While the Weinke packaging construction is more flexible and light-weight than the prior art plastic bag/chip board container combination, it requires two separate and consecutive oxygen evacuation and gas flushing steps, as well as two separate and consecutive heat sealing steps. This increases the time needed to package the piece of meat, and therefore the costs of the entire packaging operation. The Weinke inner bag must be sealed because it is used to display the meat for the customer after the oxygen-impermeable outer bag is removed to permit the meat to bloom.
Still a third construction of food packaging is a bone-guard bag previously sold by the Winpak Films Division of Flex-On, Inc., the assignee of the present invention. It consisted of an oxygen and moisture-impermeable outer plastic bag, and an inner plastic bag that was inserted into the outer bag at the time of manufacture and heat sealed into place. This preseal allowed easy opening of both the inner and outer bags simultaneously as, e.g., a piece of meat was placed inside the inner bag. This inner bag, in turn, was made from a puncture-resistant plastic film in order to reduce the likelihood that a bone in the meat could puncture the inner and outer bags to allow air and moisture to contact and spoil the meat.
While the Winpak Films bone-guard bag proved superior to competing packaging products for preserving meats, it suffered from several deficiencies. First, the inner bag proved susceptible to being punctured by bones in some instances. This caused the less puncture-resistant outer bag to become vulnerable to puncture as well. Second, the heat seal that secured the inner bag to the outer bag extended across the entire top of the bag, thereby completely sealing off the area between the inner and outer bags. This feature made gas flushing and complete evacuation of oxygen in this area impossible by the customer. Should a puncture be created in the inner bag, the oxygen trapped in this unevacuated region between the two bags could readily come into contact with the meat.